Types of Heat Pumps: What Are They, How Do They Work, and Which Is the Best for You?
A comfortable environment plays an integral role in how we spend our days, and one way to achieve it is through air conditioners and heat pumps. We are all very familiar with air conditioners, but most people are not aware that an air conditioner is a specific type of heat pump too and there are many more systems that can be used for the same purpose of heating or cooling your house.
In current times, we simply cannot do without proper heating and cooling. It is a fundamental requirement to think of temperature control when designing residential or commercial buildings. Unfortunately, this does have a downside as these requirements can come with a huge energy footprint. While some air conditioners can be energy-consuming there are various forms of heating and cooling which can be beneficial in creating an energy-efficient home.
Let us look at what those other types of heat pumps are, how they work, and how you can choose a suitable one for your needs.
What Are Heat Pumps?
Simply put, a heat pump is a device that is used to transfer heat from one place to another. It can be used for both heating and cooling purposes. It can either take heat from the inside and eject it outside (cooling), or it can take heat from outside and inject it inside (heating).
Now, there are multiple ways through which this function can be achieved; let’s go through that in detail:
Heat pumps efficiency is much higher than electrical resistance heaters. But there is a catch. This efficiency decreases as the temperature gradient or the difference between the outdoor and indoor temperatures begins to increase.
The use of the term “heat pump” can confuse most people into thinking that these devices can only heat an indoor space and not cool it. But as we have defined earlier on, they can do both jobs, often through a single appliance. This is achieved through the use of a “reversing valve” in the case of air conditioners. Through this mechanism, the condenser and evaporator coils can be interchanged i.e., the condenser can become the evaporator, and the evaporator can become the condenser, as required.
How Do Heat Pumps Work?
How a heat pump works is by moving a fluid known as refrigerant throughout different components known as the evaporator, condenser, compressor, and expansion valve. The refrigerant is the primary medium through which the heat is removed or added in the room. It can absorb heat from its environment and cool it when combined by other components such as evaporators or condenser. In the following cycle, we will be looking at how a heat pump can be used to cool a space. The same process can be reversed to get a heating arrangement.
The refrigerant is passed through an expansion valve, which converts the previously liquid refrigerant into a gas. During this expansion, the refrigerant cools down. It is then run through a series of coils in the evaporator, which are blown over with a fan. Cool air is thus injected into the room, and heat is absorbed by the refrigerant, which turns into a hot gas.
It is then run through the compressor, where it is compressed and converted into a high-temperature high-pressure gas. The refrigerant is introduced through a network of coils in the condenser and blown over by fans to remove the stored heat and eject it into the outside atmosphere. The refrigerant, which is now a liquid at this point, is cycled again through the same process to continue getting cold air.
How Does Heat Pump Work in Cooling Mode?
The liquid refrigerant is pumped through the indoor coil (evaporator), and air from inside your room is blown over it. The refrigerant absorbs heat energy, and the resulting cold air is blown back into the house. The refrigerant then evaporates into gas form.
The gaseous refrigerant is then sent to the compressor, which pressurizes it. Pressurizing the gaseous refrigerant heats it. The hot, gaseous refrigerant is then sent to the outdoor coil (condenser). The fan in the outdoor unit blows outside air over the coil. The refrigerant transfers its heat to the outside air because the outside air is colder than the refrigerant. As the refrigerant cools, it condenses back into a liquid.
The liquid refrigerant is sent to the expansion valve in the indoor unit, which reduces its pressure to cool it further. The cold, liquid refrigerant is now ready to be pumped back to the evaporator coil, and the cycle can begin again.
How Does a Heat Pump Work in Heating Mode?
In cooling mode, there is no significant difference between an air conditioner and a heat pump. However, in heating mode, the most distinctive feature of the heat pump comes into play: the reversing valve. The reversing valve reverses the flow of the refrigerant such that the heat pump releases energy into the home. Thus, the outdoor unit’s coil plays the role of the evaporator, and the indoor unit’s coil plays the part of the condenser.
The overall process stays the same. First, liquid refrigerant is pumped through the outdoor coil (evaporator), and outside air is blown over it. Then, after the refrigerant absorbs heat energy, the resulting cold air is blown outside. The liquid refrigerant then evaporates into a gas.
The gaseous refrigerant is passed through the compressor, which pressurizes it to heat it. The gaseous refrigerant is then sent to the indoor coil (condenser). The indoor fan blows cold, inside air over the gaseous refrigerant. Since the indoor air is colder than the gaseous refrigerant, the refrigerant loses heat to the indoor air. The resulting hot air is blown into the house.
Meanwhile, the refrigerant condenses into a liquid and is then pumped to the expansion valve, depressurizing it to cool it down further. Finally, the cold, liquid refrigerant is pumped to the outdoor coil (evaporator), so the cycle can start over again.
1. Heat Pump Type: Air to Air Heat Pumps
As evident, air-to-air heat pumps work by using air as a heat sink and a heat source. Common examples of such systems are residential and commercial air conditioners. These systems are also reversible, which means they can either be used for heating or cooling.
Air-to-air heat pumps are energy-efficient air conditioning systems, with cheaper installation and upfront costs than other heat pump systems. They can provide sufficient heating and cooling in climate zones and are thus suitable for use in large parts of the country.
There is, however, a downside to these heat pumps. Their efficiency decreases as the temperature difference between the indoor and outdoor temperature increases. In extreme cold or extreme heat, air-to-air heat pumps can face some difficulty in operating as desired. In freezing climates, this can especially be a problem and hamper air conditioning operations. However, the freeze protection feature in some heat pumps can significantly help to keep your pipes from freezing in extreme cold at a low cost.
There are a few different types of air-to-air heat pumps. Let’s see each of them below:
a) Mini-Split Heat Pump (Ductless Heat Pump)
Mini-split heat pumps are rising swiftly in popularity across residential and, indeed, commercial consumers, due to their ease of installation, flexibility, and energy efficiency. In fact, they can be made even more energy efficient when coupled with a smart AC controller. These types of heat pumps do not require an extensive network of ducts or vents and are suitable for retrofits where older structures need to be fitted with a modern air conditioning system.
These systems consist of two parts, an indoor unit, and an outdoor unit. The outdoor unit houses the condenser, which ejects the undesired heat outside, while the indoor unit throws in cool or hot air into the room.
A mini-split outdoor unit can also be used to power multiple indoor units, giving rise to what is known as multi-zone mini-splits. Through this method, individual units can be controlled independently in what is known as “zoning.”
Freeze Protection (FP) mode in Cielo Breez Smart AC control
Freeze Protection mode is a unique and innovative feature for those having homes in extremely cold climates. With Freeze Protection, you can maintain a comfortable temperature in the indoor space even when it is not in use.
The air conditioner can run at a low power heat mode, ensuring that the room does not get unbearably and freezingly cold. This mode is ideal for when you are not occupying the space, but also do not want it to freeze over or get really cold
b) Exhaust Air Heat Pump
A lesser-known variant of air-to-air heat pumps is exhaust air heat pumps, which uses exhaust air from a separate process and extracts heat from it. Requirements for such a type of heat pump are that it should be located close to an exhaust system with constant flow and also consistent temperatures.
2. Heat Pump Type: Underwater/Underground Heat Pumps
As discussed above, a disadvantage of air-to-air heat pumps is the temperature variation observed in the environment. Among the different types of heat pumps, underground or underwater heat pumps eliminate this problem because the ground has a near-constant temperature throughout the year. Hence underground or underwater heat pumps provide efficient cool or warm air all year round. Moreover, heat pump efficiency for this type is much greater than the other types, due to their low energy consumption.
a) Water Source Heat Pumps
Underwater heat pumps use a water source as the heat exchange medium. But a pre-requisite is, of course, that a water source is located nearby. These heat pumps can work as reversible heat pumps too, absorbing heat from the water to heat the inside environment, and also releasing heat absorbed from the inside to the body of water.
This is achieved through a series of coils or loops placed under the body of water. Refrigerant, in some cases, water itself, is pumped through those coils and then routed inside the home to provide heating or cooling.
As mentioned before, underwater temperatures remain stable throughout the year, and water source heat pumps can be put to good use in extreme climates as well without a drop in performance.
Even though underwater systems do not require extensive preparation by digging up the ground (as is the case with geothermal systems), they are still cost-intensive initially as compared to air-to-air systems.
A further distinction in underwater systems can be made, namely open loop and closed loop systems. A closed loop system has a refrigerant inside of it, which is constantly recycled through the piping network. The refrigerant does not need to be replenished again and again. Open loop systems, on the other hand, take in water from the water source and pump it inside the home. This water is then ejected back to the water source. The same quantity of water is not continuously pumped through the network. Water source heat pumps are thus the right choice for rural homes near bodies of water.
b) Ground Source Heat Pumps
Also known as Geothermal Heat Pumps, these systems use the heat of the ground instead of water to heat or cool an inside space. The ground is also a near-constant temperature heat source throughout the year and can be dependent upon for heating and cooling needs. Same as underwater heat pumps, a refrigerant is passed through coils and loops that are placed underground. This refrigerant is then pumped inside the home, where heat is exchanged.
In the summers, this means that the refrigerant transports cool refrigerant inside the home, where it absorbs heat from the indoor space and heats up, while the house cools down. The reverse is true during the winters when the refrigerant ejects heat into the room while cooling down itself.
The underground pipes can be laid in a number of configurations. They can be placed in horizontal loops under the ground or can be drilled vertically to greater depths in pipes. These U-shaped pipes are connected at the bottom, forming an interconnected network.
3. Heat Pump Type: Hybrid Heat Pumps
In very cold climates, a heat pump can run into trouble because of the massive temperature difference between the outdoor temperature and the desired indoor temperature. This is especially true for air-to-air systems, which can stop working at temperatures close to freezing, necessitating the use of furnaces, which are an added expense.
Moreover, even though geothermal and underwater heat pumps can work at a wider temperature range, they are better at cooling than heating.
To combat this issue, you can use hybrid heat pumps. These systems are a combination of two different types of heat pumps, each suited to different climate conditions and requirements. An example of such an arrangement is of solar-powered heat pumps. They use solar power as a source of energy to power additional heating systems or can be used directly to provide heating by harnessing the sun’s energy.
In a Nutshell – Which Type of Heat Pump is Best For You?
Whatever system you choose among the different types of heat pumps, be sure to have a complete picture of the climate zone you are in, your budget, requirements, and of course, the location of your heat pump. If you are retrofitting an old, existing building, you’d be better suited to go for a mini-split heat pump. But if you live close to a large body of water in a rural area, a geothermal or underwater heat pump might be worth a look.
Apart from personal preference and geographical limitations, it is important to keep an eye on the installation and operational costs. As discussed before, a geothermal system will be costly to install, but the operating costs can be extremely low, as compared to a ductless heat pump. But on the other hand, a ductless system will be much cheaper to buy and install, with minimal installation times as well.
If you believe in going the extra mile to achieve greatness, then Cielo Breez smart AC controllers are your destination. These ultra-modern smart devices incorporate smart functionality into your ductless heat pumps or air conditioners. Relish the ingenuity of the smart HVAC industry with Cielo Breez to reflect comfort, control, and convenience in your air conditioning experience.